Chromatographic apparatus



March 17, 1970 1 E HALL ET AL CHROMATOGRAPHIC APPARATUS Filed April 21, 1969 United States Patent O 3,500,617 CI-IROMATOGRAPHIC APPARATUS Joseph E. Hall, Richard J. Hunt, and Colin J. Vincett,

Cambridge, England, assignors to Pye Limited, Cambridge, England, a British company Filed Apr. 21, 1969, Ser. No. 817,647 Claims priority, application Great Britain, May 2, 1968, 20,921/68 Int. Cl. B01d 15/08 U.S. Cl. 55-386 12 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an apparatus for the injection of samples into a gas chromatograph column. The invention provides a magazine for storing slugs containing the samples, a mechanism for transferring the slugs individually into a region at the mouth of the chromatograph column, means for passing a sample contained in a slug into the column and an ejector arrangement for ejecting the spent slug from the column when the sample, or a part of it, has passed into the column.

The present invention relates to chromatographic apparatus and more particularly to apparatus for the injection of samples into a gas chromatograph column.

According to the present invention, apparatus for the injection of samples into a chromatograph column comprises a magazine for storing a plurality of slugs, each containing a sample to be injected into the column, means for individually transferring the slugs from the magazine into a region at the mouth of the chromatograph column, means for causing at least a part of the sample in a slug to be passed into the column and ejector means located in said region at the mouth of the column for ejecting a slug from the column.

The region at the mouth of the column may contain a heater for the evaporation of the sample material from the slug so that it may be conveyed by a carrier gas through the column.

Advantageously the magazine stores the slugs one above the other and the slugs may be transferred from the magazine to the column by means of a plunger operated by electromagnetic means which can be operated to cause the plunger to eject a slug from the magazine into the column and which is then operated to retract the plunger and allow the next slug to fall into the position for subsequent ejection from the magazine by the plunger.

Preferably the ejector means is also operated by electromagnetic means, and after a sample has been removed from a slug located in the region of the mouth of the column, the slug is ejected by operation of said ejector means through a guide tube into a receiving vessel in which the spent slugs are contained.

According to a feature of the invention the electromagnetic means for operating the plunger to eject a slug from the magazine and for operating the ejector means to eject a spent slug from the column are energised by the discharge of a capacitor.

Preferably the slugs are made of a non-reactive material such as glass and the sample contained therein may be either a liquid or a solid. Where the sample is a solid, the slugs may be open-ended with the sample coated on the internal wall of the slug. Where the sample is a liquid the slug is preferably closed and has a weakened portion which is broken when the slug is transferred to the region of the mouth of the column, in order to release the sample into the column.

Alternatively the slugs may be made of a magnetic material or of such a metal coated with glass.

The invention will now be further described by way of example with reference to the accompanying drawings in which:

FIGURE l shows in diagrammatic form one embodiment of slug injection apparatus according to the invention,

FIGURE 2 is a sectional view on a larger scale of the region at the mouth of the column,

FIGURE 3 is a sectional view, showing one shape for the slug,

FIGURE 4 is a scrap view of a modified embodiment, and

FIGURE 5 shows a control circuit for the electromagnetic means.

Referring to FIGURES 1 and 2, the apparatus is designed to inject repetitively small quantities of non-volatile materials onto a chromatograph column. Each injection can be of a different substance which means that numerous dilferent samples may be processed automatically. If desired, the samples may be inserted in the slugs and the slugs loaded in the magazine during a working period and the apparatus operated automatically during a non-working period, e.g. overnight, so that the analysis of the samples by the chromatograph column takes place during this period.

The injection of slugs into the column from the magazine can be controlled either from a control unit, or by means of a chromatograph address system, by a computer or by a combination of these means.

The slugs 1, preferably made of glass, are contained in a magazine generally indicated at 2 consisting of two spaced rods 3 defining a slot in which the slugs are located and along which they are guided. To this end, as shown in FIGURE 3, the slugs 1 may be provided with a waist 4 which engages with the rods 3.

The slugs 1 are successively transferred from the magazine 2 into the region 5 at the mouth of the column 6 by means of a double-acting solenoid operated plunger 7. When one coil 7a of the solenoid is energised by a capacitor discharge, the plunger 7 pushes the bottom slug from the magazine 2 down the tube 8 into the region 5 at the mouth of the column. The plunger is retracted when the other coil 7b of the solenoid is energised, thereby allowing the slugs to fall down the slot so that the next slug is positioned for subsequent ejection from the magazine by the plunger.

The region 5 at the mouth of the column contains an ejector/location tube 9 which receives the slug and is surrounded by a heater coil 10 which heats the slug to evaporate the sample which is then carried into the column for analysis, by the carrier gas supply which is fed into the column at 11. The ejector/location tube 9 is also surrounded by an ejector coil 12 which can be pulsed by a capacitor discharge so that it sets up a short duration magnetic field in the ejector/location tube to eject a slug from which the sample has been removed.

The magnetic eld set up by the capacitor discharge in the coil '12 causes a magnetic ejector device 13, which normally rests on abutments 13a, to accelerate upwards towards the centre of the field, and accordingly a slug which rests on the top of this device 13 is also accelerated. When the ejector device 13 has travelled a predetermined distance inside the ejector/location tube 9 it is restrained by a stop 14 at its lower end engaging abutments 13a and falls back into its original position. The slug however continues in its path through the guide tube 15 into the receiver 16. Preferably only the lower part of the ejector device 13 is made of magnetic material, the upper part being made of non-magnetic material. This ensures that the magnetic lield from coil 12 draws device 13 suf- 3 iciently far up the tube 9 to give the necessary impetus or the slug 1 to be ejected into the receiver 16.

The ejector/location tube 9 consists of a thin walled ube which is placed inside the column. It serves to mainain the slug in a vertical position so that it does not otate end-for-end on entering the column and foul other arts of the apparatus. It also maintains the slug at he predetermined level in the column, with respect to he heater and ejector coils 10 and 12, and houses and onstrains the ejector device. The ejector location tube nay have holes or slots drilled in it and may be glass oated or made of glass. The ejector device 13 may be :lass-coated. Alternatively the location tube and/or the :jector device may be made of metal and coated with tationary phase material to reduce their activity.

In some cases it may be desirable to introduce either iquid or solid samples into the injection chamber of the :olumn in sealed glass slugs. Such slugs may be made vith a weakened neck portion so that this portion breaks .way on falling into the injection region 5. As shown in 2IGURE 4, in order to prevent fragments of glass enterng into the mouth of the column which might eventually lock the column, the slugs from the magazine are .llowed to fall into a receptacle 17 of magnetic material raving a mesh bottom 18. This receptacle is located in he region of the heater and injection coils as previously lescribed.

In operation, when a glass slug falls into the receptacle, he weakened portion breaks and the sample is evaporated y the heater coil 10 and swept into the column by the :arrier gas liow. In order to eject the spent slug and the :lass particles, the eject coil 12 is energised which has he efect of accelerating the receptacle 17 upwards until t contacts the stop 19. The receptacle '17 is restrained tnd falls into its previous position, but the spent slug and my fragments of glass have sufcient momentum to pass hrough the guide tube into the receiver 16.

In another embodiment, used for example in the inection of volatile fluids onto the column, a slug such as hat shown in FIGURE 3, with a tubular envelope of lastics material, such as PTFE, crimped or sealed at both :nds to contain the sample, may be used. In use the pres- .ure generated within the plastics envelope, due to sample 'aporisation on heating, ruptures this tube and releases he enclosed sample into the carrier gas stream.

FIGURE 5 is a simple diagram of a circuit which may )e used to provide the capacitor discharge for energising he coils of the plunger 7 or the coil 12. The circuit comlrises a capacitor C which can be selectively` connected :y means of changeover switch S, either to a charge cir- :uit comprising a D.C. source and a charging resistor R; )r to discharge through a coil L which represents one of he aforementioned coils. The switch S may be operated nanually, or automatically from a control unit or a comluter programme.

The apparatus according to the present invention pos- .esses the following advantages:

Firstly, where glass or glasscoated slugs are used the .torage and evaporation of materials upon glass gives an ncreased stability of the samples over the case where netal slugs are used. Moreover, the slugs can accept large njections of relatively dilute solutions and concentrate he solution by the evaporation of solvent. Furthermore, he slugs are untouched by any apparatus which may be :ontaminated once they have been loaded into the magazine. The slugs are maintained cool in the inert atmoshere of the carrier gas. Also, the use of a capacitor dis- :harge to energise the ejection coil provides high power vithout requiring heavy duty wiring and eliminates eld twitching problems.

We claim:

1. Apparatus for the injection of samples into a chronatographic column comprising a magazine for storing a plurality of slugs, each containing a sample to be injected into the column, means for individually transferring the slugs from the magazine into a region at the mouth of the chromatographic column, means for causing at least a part of the sample in a slug to be passed into the column and ejectormeans located in said region at the mouth of the column for ejecting a slug from the column.

2. Apparatus as claimed in claim 1, wherein said ejector means is made partly of a magnetic material and is operated by electromagnetic means to eject a'slug from th mouth of the column.

3. Apparatus as claimed in claim 2, wherein the slugs are ejected through a guide tube into a receiving vessel.

4. Apparatus as claimed in claim 1, wherein the region at the -mouth of the column contains a heater for evaporating the sample material from the slug, and means for applying a carrier gas to convey the sample through the column.

5. Apparatus as claimed in claim 1, wherein said magazine stores the slugs one above the other and the slugs are transferred from the magazine to the column by means of a plunger operated by electromagnetic means which can be operated to cause the plunger to eject a slug from the magazine into the region at the mouth of the column and which is then operated to retract the plunger and allow the next slug to fall into the position for subsequent ejection from the magazine by the plunger.

6. Apparatus as claimed in claim 5, wherein the electromagnetic means for operating the plunger to eject the slugs from the magazine and for operating the ejector -means to eject a slug from the column are energised by the discharge of a capacitor.

7. Apparatus as claimed in claim 2, where in the region at the mouth of the column contains an ejector/location tube in which an ejector device is located, said tube being surrounded -by a heater coil to evaporate a sample from a slug located in said tube and resting on said ejector device and also by an ejector coil which is energised to attract said ejector device upwards to cause it to eject a slug from the column.

8. Apparatus as claimed in claim 7, wherein the ejectoi" device rests on an abutment in the ejector/location tube and is provided with a stem portion extending below said abutment and terminating in an enlarged end for-ming a stop for engaging the lower end of the abutment, in order to restrain upward movement of the ejector device when it is attracted upwards by energisation of the ejector coil.

9. Apparatus as claimed in claim 8, wherein only the lower part of the ejector device is made of magnetic material, the upper part being made of non-magnetic material.

10. Apparatus as claimed in claim 7, wherein the ejector/location tube is provided with holes or slots in its walls.

11. Apparatus as claimed in claim 7, wherein the ejector/location tube is made of glass or glass coated material and the ejector device is also glass coated material.

12. Apparatus as claimed in claim 2, wherein the mouth of the chromatographic column is formed with an enlarged portion surrounded by a heating coil and an energising coil and said enlarged portion supports an ejector device in the form of a receptacle provided with apertures in its lower surface, and inwardly directed stops are provided on the walls of said enlarged portion above the ejector device to limit its upward `movement when attracted upwards upon energisation of the energisation coil.

References Cited UNITED STATES PATENTS 3,063,286 11/1962 vNerheim 55l97 X JAMES L. DECESARE, Primary Examiner 

